Keeping Manufactured Housing Installers Informed!

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While a variety of materials are used as exterior wall coverings for manufactured housing, vinyl siding might be the most common. So, let’s look at some of the issues that are often overlooked regarding vinyl siding installation.

Everybody knows that vinyl siding expands and contracts with changing weather conditions, Experts say a single 12’ long piece of siding can be expected to grow or shrink up to 5/8” in length. You must allow for this movement as you install the siding on the home. Here are some key points to consider:

Siding box instructions, leave 1/32″ under nail head or staple crown to allow the siding to expand/contract.

Vinyl siding should be “hung” on the side/end walls of the home. When installing nails or staples, be sure to leave at least 1/32” (thickness of a dime) between the nail flange and the nail head or staple crown.

For horizontal panels and accessories, start installing fasteners in the center of the panel and work towards the ends. Install the nails/stapes in the middle on the nail slot. Don’t angle the fastener or use it to pull on the panel.

For vertical applications (including corner posts and “J” channels) along the sides of windows and doors, apply the first nail or staple at the top of the top most nail slot (to keep it from slipping down) and the remainder of fasteners in the center of the nail slot.

Fastener spacing is generally 16” apart for siding panels, and 12” apart for channels and accessories. If the slots and framing studs don’t align to allow you to center the fastener, use a slot punch tool to enlarge the slot,

When installing a new manufactured home, the manufacturer will be providing you with the proper nails or staples to install the siding. But, for a relocated manufactured home it will be up to you to determine that you have the right fastener for the job. In all cases, the fasteners must be corrosive resistant, such as aluminum nails, galvanized roofing nails, or galvanized staples.

Look closely, these staples are galvanized to resist corrosion.

Also, be sure the fasteners are the proper length, about 1 ¼” of penetration into the framing of the home. If the home is sheathed with OSB (oriented strand board) or some other nail-able sheathing, you can generally install some fasteners in the sheathing, but be sure to make an effort to hit every framing studs. If you are installing siding over a foam insulation, you will need longer fasteners in order to achieve the 1 ¼” penetration needed.

The thing that I believe is most overlooked in regards to vinyl siding installation is the need for utility trim. Also called finish trim or under-sill trim, it’s needed to secure the siding wherever the nailing flange has been removed, most notably under windows or doors. The utility trim should be cut about ¼” shorter than the section of nail flange that has been removed, and fastened directly to the wall, under the window, door, etc. Using a snap lock punch, punch lugs every 6” along the cut edge. When installing the panel, slip the cut edge into the utility trim to secure it in place. If your manufacturer is not providing or using utility trim, start requesting it!

Siding panels should be cut and installed allowing for about ¼” gap between the panel and the inside of the receiving “J” channel, corner post, backer block, etc.

Siding panels should overlap each other by 1” to 1 ½”. If you have to cut off the factory pre-cut edge, be sure to notch both the nail flange and the bottom lock to allow for lateral movement of the siding.

If the factory end is cut off, be sure to re-notch the bottom of the siding panel as well as the top!

Be sure to stagger the joints by about 12” unless separated by three courses. Don’t use short pieces that cannot be fastened to two studs. This is particularly true along the gable end, under the overhang on the end walls. The very last piece of siding at the gable can be fastened with an aluminum trim nail. Drill an 1/8” hole and don’t drive the nail tight. Snug will do it! This should be the only exposed fastener needed for siding application.

Be sure to leave enough nail flange to allow attachment at 2 studs!

Ok, that is enough for now. As always, be sure to follow the actual siding installation manual and product instructions! We will discuss this topic further in our next post!

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When the Manufactured Housing Improvement Act of 2000 established both an Installation Program and a Dispute Resolution Program, the responsibilities and liabilities for installers increased significantly. One of the added responsibilities was the requirement for installers to maintain records for any new manufactured homes they’ve installed. So, let’s take a look at the issue of installer record keeping as more than a regulatory obligation, but also from the standpoint of being a good business practice.

If you are an manufactured home installer in one of the 14 states where HUD operates the Installation Program, or the 24 states where HUD runs the Dispute Resolution Program, you are required to maintain records of the homes you install for a minimum of three years. If you are in a state that operates their own programs, it is likely that your state has a similar requirement.

So what type of records should an installer keep? The Manufactured Home Installation Program regulations (24 CFR 3286.314) clearly lays out what records the installer must maintain where HUD oversees the installation. Below is a summary of the requirements:

(1) The name and address of the person with whom the installer contracted for the installation work and the address of the home installed;

(2) The contract to which the installer performed the installation;

(3) Any notice from an inspector disapproving the installation work;

(4) The qualified inspector’s verification of the installation work;

(5) The installer’s certification of completion of installation;

(6) Foundation designs used to install the home

While maybe a good start, this would be the minimum that should be kept. Should you ever have to defend your installation job, you will need better records. So, let’s make a new list of documents that every installer should have in their files:

The Building Permit Cover Sheet. I am a big fan of organizing the installation documents to provide to the building code official, and to better aid the installer in pre-planning the job. Click here for A Tool to Improve the Building Permit Application Process (from the blog on March 26, 2018).

The Complete Installation Checklist which is found towards the back of every installation manual. Or even better, the Expanded Installation Checklist (from the blog on Oct. 16, 2017) that is more detailed and covers most issues that you should be checking before driving away from the home. These checklists are going to be your best friend should you ever find yourself in the middle of a dispute.

Pictures are critically important. If you are digging footings below the frost line, how about a picture of the excavation along with a tape measure so you can show the depth? Also take pictures of the completed job. We all know that homeowners often change the landscaping around the home, or add decks, patios, etc. You want to be able to show the situation of the site grading when you certified the installation.

As a trained and licensed manufactured home installer, you know how important it is to report any problems or defects to the retailer or manufacturer. It is equally important for you to keep notes of all problems that you observed and reported.

Crossovers don’t line up? Report to the manufacturer!

Speaking of problems that you’ve reported, if the manufacturer authorized you to make repairs on their behalf, be sure to have a note to that effect in your file and a copy of the detailed invoice you submitted.

Did the fuel provider conduct the gas line testing? Make sure you give them with a copy of the required test procedures (from the installation manual), and get a written receipt from them proving the testing was successful for your file.

If you used an alternative anchoring system to stabilize the home, that is great. But be certain you have a DAPIA detail from the manufacturer showing their approval of the system.

It goes without saying that you will keep the designs taken from the installation manual illustrating the foundation construction, but make sure those details include notes specific to the home site. Such as soil bearing capacity, or depth of frost penetration. Indicate how you obtained this information.

I think by now you get the picture. I know that very few installers are keeping records of the manufactured homes they install. But that needs to change. We all need to take a more business minded approach to installation. When the day comes that you will need to defend your installation, you will be glad you started keeping records!

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In our last post we talked about how added structures, such as carports, patio covers and the like, add unintended vertical loads to a manufactured home. Today, let’s talk about how added structures subject the manufactured home to increased horizontal (wind) loads, and the possible damage that can occur as a result.

Another example of a patio cover improperly attached to a manufactured home.

The biggest problem that I have seen is when an awning, carport or patio cover is attached directly to the fascia board of the manufactured home. Typically, the fascia board on a manufactured home is attached to the roof trusses without anticipation of a large attachment. Studies has shown that the manufactured home can easily withstand the required wind loads when the home is anchored according to the manufacturer’s installation instructions. But when a carport or patio cover is attached to the fascia board, it can subject the home to significantly higher loads than the home is designed for.

This warning is found in every typical manufactured home installation manual

A quick review of the installation instructions for a few different awnings, carports or patio covers (common in the manufactured housing industry), shows that they agree that the awning should not be attached to the fascia board. However, there remains a concern as they suggest their products can be attached to the actual roof rafter or wall stud of the home (no mention of type of home, manufactured home or otherwise). I found no mention of fastening the mounting rail to a roof truss as opposed to a roof rafter. Nonetheless, I feel very safe in stating that the home manufacturer did not design the roof truss to support an awning, carport, porch canopy, or similar accessory.

Most critical is when the wind gets under these structures an they start to tear away from the home. As they break free, they create openings that allows the wind to get into the roof cavity, which can lead to catastrophic failure. Take a few minutes and watch these two videos. I think they make a pretty convincing case.

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A while back we talked about all of the different issues that a professional manufactured home installer needs to know regarding the marriage walls. I thought we should revisit that issue and focus only on the fastening together of the two halves to make the home a single, solid, integrated structure. Since this is a big topic, I think I will split things up and only discuss the fastening of the floors and walls. Let’s save the roof for a future date.

Your goal should be to make the joint between the home sections as tight as possible. There should be no gaps, and the fasteners must be installed per the manufacturers installation instructions. These fasteners should not split the lumber and must have adequate penetration to secure the home.

Remember that assembly of the home is critical to the home’s ability to survive high winds. A two (or three) section manufactured home must be able to transfer wind loads across the marriage line to the specific walls designed to accept these loads (shear walls), and ultimately into the ground through the anchoring system. Spaces, gaps, voids, etc., between the two sections, can prevent the home from safely handling these loads.

This gap must be shimmed!

It goes without saying that you need to remove all shipping materials (plastic, straps, nails, staples) while you can still access them. Next, look over the marriage line gasket for damaged areas and add new gasketing material where needed. Ask the manufacturer to supply a decent length of extra gasket material to do this.

Look closely where the staple keeps the sections apart.

If you have attended any of my training classes, you know that I think the marriage line gasket is the weakest point in the entire design of a manufactured home. Take a few minutes to make sure the gasket can do its intended job. Consider offering better options, if possible. We can talk about this idea in a future post.

Never work under a suspended load! Support the home with cribbing every time!

Be sure to protect yourself and others at the job site. Use cribbing or other support devices in the event that a home section should fall. Never allow a situation where a worker could be crushed or worse.

For new manufactured homes, the manufacturer will be providing all the fasteners necessary to secure the home sections. If you are not receiving these fasteners, you need to have a serious talk with someone at the factory.

Bring the home sections together as tight as possible. Any gaps between the sections must be shimmed! The manufacturers all say that if the gap is wider then 1”, you need to reposition the home to reduce/eliminate the gap. Any shims used at the marriage line are generally ¾” thick lumber, wide enough to accept the fastener without splitting. I favor a ¾” x 2 ½” pine firring strip. Be careful not to pull the rim joist away from the floor joists. The same is true at the roof ridge. Don’t pull the top rail or ridge beams away from the roof truss. Ultimately, the fasteners you install should just hold the home tightly together, not be pulling the sections tighter.

In general, most manufacturers (for homes in wind zone 1) require lagging the floor sections together using a lag screw and washer at each floor joist bay, and staggered from side to side. The lags may be installed at an angle (toe screwed), but not so much of an angle to reduce how far the lag goes into the other joist. You can also drive them straight into the floor joist, but that leaves a bigger hole in the bottom board to repair. At least 1 ½” penetration into the receiving joist is required.

These lags should be staggered and the bottom board patched!

Seal the bottom board with bottom board tape after the lagging is completed. Some manufacturers require additional fasteners at the ends of the home and at any through-the-rim heat duct connection. Be sure to check the manual, specific for the home you are installing.

This manual requires additional fasteners at the floor of the home.

Fastening of the walls is getting a bit more complicated with several manufacturers providing different options. Most installations I see still use wood screws (#10 x 4 ½”) 24” apart from the bottom plate to the top plate of the wall. Be careful using lag screws as they can split the wall studs.

Likewise, you need to fasten the marriage line along any openings or door ways with the same fasteners and spacing. I have been seeing some manufacturers sending brackets or plates for fastening the marriage line. Be sure to use the right number of nails per bracket and that you use appropriate length common nails. Not finishing nails, aluminum nails, roofing nails, etc.

Brackets at marriage line opening

Hopefully, this will encourage you to reexamine how you assemble multi-section manufactured homes. Make sure everyone on your crew understands how important this is! We will talk about roof fastening at a future date.

As always, refer to the specific manufacturers installation instructions for every home you install!

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If you’re like me, you can never have too many tools. But to properly and safely install a manufactured home, there are some special tools that you need to use. I though it might be helpful to put together a list of the top 11 things that every professional installer should have at every job site.

Angle finder with a magnetic base.

We all know that when installing ground anchors, the angle of the straps cannot exceed 60°. Be sure you have a tool to measure the strap angle to be certain your strap angle is correct. If you don’t have one, purchase an angle finder and start checking the straps angle. By the way, it is always smart to snap a picture for your installer file!

A continuity tester.

You know that ever installation manual requires that you perform a continuity test on all metal parts in the home that could possibility become energized. Metal parts like the chassis, heat ducts, metal light fixtures, gas lines, water heaters and furnaces, metal siding or metal roofs, range hoods, etc… A continuous path to ground must be present and you need to perform this test to verify all of these metal parts are grounded.

A continuity tester is a must!

A circuit tester with a GFCI trip button.

This allows you perform the required operation test throughout the home as well as test GFCI outlets, and assure that any slave receptacles (receptacles downstream of the actual device) are protected as well. This is also an easy way to check the operation of any switched receptacles.

An apparatus to perform a water supply line pressure test.

This device is probably going to have to be fabricated from plumbing parts. It must include a gauge that can measure pressure, and inlets with shut off valves to allow you to introduce water and air pressure into the water piping. Remember to remove the source of air when conducting the test.

A manometer (or other testing gauges that measure in increments not greater than 1/10 lbs.) to conduct gas line testing.

By now you should know about the two required gas line tests; the high-pressure test (3 psi) that checks the piping and the low-pressure test (6-8 oz or 3/8 to 1/2 psi or 10” to 14” of water column) that checks the entire system as well as the connections to the appliance. Again, this may be an apparatus you assemble yourself, or maybe purchase an electronic, digital version. If someone else (like the fuel provider), performs this test for you, make certain to provide them with a copy of the proper test procedures from the installation manual, and get receipt or other written proof that the test was conducted for your files.

GFCI protected extension cords.

Working in often damp or wet conditions, with a great possibility of cords being stepped on, frayed or otherwise damaged, you want to reduce the risk of electric shock hazzard. All extension cords must be equipped with Ground Fault protection.

A thermometer to check the water temperature at each of the bath tubs, bath tubs/showers or showers.

Run the water in each tub or shower fixture for 1 minute at the hottest setting and use a thermometer to assure that the water temperature is not greater than 120°. While the fixtures are generally pre-set, I have seen defects that allowed the water temperature to exceed 120°. Don’t take the risk, test the fixtures.

A glue bottle.

In the event that you ever need to replace a wall panel, section of the ceiling, or a section of the floor decking, it is critical for you to glue the panel or decking to the framing members. A ¼” bead of PVA glue (white glue) is generally sufficient.

Go/No Go Gauges for water supply lines.

If you ever have to install a crimp ring on a water supply line, you need to assure that the crimp is done properly and Go/No Go gauge is the only way to do that!

Safety Glasses

Everyone working at the job site must wear safety glasses. Having a few extra pairs handy is a great idea. If your crew likes to wear sunglasses on the job site, make sure that they are equipped with shatter resistant lenses and side shields.

First Aid Kit.

Every good set crew has a fully equipped first aid kit available. If you don’t have one, a basic kit runs only about $30.

I am sure that there are some other important tools that I am forgetting. Feel free to drop me a message if you can add to this list.

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Looking over a recently revised manufactured home installation manual, (DAPIA approved in Feb. 2018), I ran across something that I thought was worth a closer look.

In the section of the manual that talks about footings, I found a chart titled “Foundation Embedment Factors for Cohesive Soils” (there is also a chart for Non-Cohesive Soils).

In case you are wondering, cohesive soils are described as clay, or soil with a high clay content, which has cohesive strength. Cohesive soil does not crumble, can be excavated with vertical sides, and is like plastic when wet. Cohesive soil is hard to break up when dry and sticks together when submerged. Cohesive soils include clayey silt, sandy clay, silty clay, clay.

Cohesive Soil

On the other hand, non-cohesive soils are loose soils like sand, or sandy soils.

Ultimately, by using these charts and directions, you can increase the maximum load per footing based on the depth that the footing is embedded in the soil.

Let’s try to work through the process. This manufacturer tells me that a 14’ wide home, in the south (20 psf) roof load zone, with piers spaced 8’ apart, has a pier load of 5640 pounds (per pier).

Since I like to auger round footings, the chart for circular shape footings says that I need a 28” round footing at a soil bearing capacity of 1,500 PSF. But my auger is only 24” diameter! Well, this is where the “Foundation Embedment Factors for Cohesive Soils” chart might come in handy!

Since I can only dig 24″ round footings, I need to start there. The chart for circular footings tells me that a 24” round footing can carry 4710 pounds (again 1,500 Soil bearing capacity). I know my 24” round footing will be 36” deep (for example, to get below the frost line) in a clay (cohesive) soil, so I can multiply the 24” footing capacity by the 1.56 as indicated in the cohesive soils chart and my 24” footing works! (4710 pounds x 1.56=7347 pounds, well beyond the 5640 pound load needed to support the home).

It is not as confusing as it seems. You just need to know if your soil is cohesive (clay) or non-cohesive and know the footing size and depth. Use the chart to determine the embedment factor and multiply the footing capacity by the factor from the chart.

A few important things to consider before you start reducing footing sizes. Currently, this is specific to only a few manufacturers. You need to check with the Quality Control Manager at your factories to see if they allow you to utilize embedment factors. One manufacturer told me that they provide these designs only upon request.

Next, you need to have a very thorough understanding of the soil at the job site. You need to have all of your documents in order and make certain that the building code official (and possibly the purchaser) understand how you are calculating these footings sizes/loads. As always, keep good records for your installation files, including copies of these charts.

While I am not an engineer, I do think that the embedment factor is to be applied only to poured in place concrete footings. But you can verify that with the factory.

Finally, on the one manual I reviewed, there is a big typographical error, labeling the chart for non-cohesive soils, so be cautious. Stay in touch with Quality Control folks and watch for further changes to the manuals.

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I know that all too often we take for granted the importance of that black, plastic-like material that stretches under the floor of manufactured homes. Some folks, (and the manufacturer’s installation instructions), call it bottom board. Others call it “underbelly” or “belly board” or some other name, but for today, lets just call it “bottom board”.

Obviously the bottom board is needed to secure and protect the floor insulation, and keep critters out of the floor cavity. But that is only half of the story.

I am certain that you have had your customers ask you why the holes cut in the floor decking for drain lines are often over cut. Why does the factory cut 2 ½” holes for a 2” pipe? What about the big hole for the bathtub “P” trap? We all have seen homeowners stuff insulation around these pipes in an effort to reduce heat loss. But is this necessary? Not really!

Leaking “P” trap was fixed, but the installer failed to replace the insulation and repair the bottom board!

If you look under the floor decking, you will see cables, drain lines, water supply lines and most likely, un-insulated metal heat ducts. These un-insulated heat ducts keep the entire floor system warm in the winter, and prevent the water pipes from freezing. Since the floor cavity is in a sense “conditioned space” those holes in the floor decking are not a path of heat loss or air infiltration. So, what keeps the outside, unconditioned air from getting inside of the floor cavity? The Bottom Board!!

Water lines in the floor. Be sure to replace the insulation and access panels to keep from freezing!

The bottom board acts as the pressure envelope, which is the primary air barrier to limit air leakage. With that in mind, we should start thinking about the bottom board as less of a part of the transportation system, and more of a thermal component which is critical to the overall performance of the manufactured home’s energy efficiency!

The red line represents the pressure envelope that is intended to contain the conditioned air inside the home.

Consider the impact of every hole, slice, cut, tear or missing access panel of the bottom board. They all allow unconditioned air to enter the floor cavity. This unconditioned air can cause significant damage to the home. In summer months, it can cause condensation to form on the heat ducts, and promote the growth of mold and mildew. In the winter, it can cause higher heating bills, and could impact consumer comfort.

The manufacturer’s installation instructions all require the installer to “Repair and Seal Bottom Board”. For new homes, make sure you inspect the bottom board upon delivery, and report any holes, tears or road damage to the manufacturer. If you need to make any repairs, follow the information in the manufacturer’s installation instructions. Replace missing, wet, damaged or dirty insulation. Allowing wet insulation to dry out does not make it as good as new, it must be replaced. Just be sure to maintain the same R value as was originally installed in the floor.

Tape over lag bolts with an approved bottom board tape.

Make certain that the material you use to make any repairs or patches are appropriate for the job. I know a lot of installers use “Flex-Mend” with great success, and it is approved for this application. If the area to repair is too large, use staples and a backer board of ¼” plywood or similar materials. On multi-section homes, you should tape over the lags used to secure the floors together.

Be sure to clean the surfaces where the patch is to be applied. The HUD Code clearly states that any patches must be just as durable as the original bottom board material, see 24 CFR 3280.305(g)(6). Duct tape is not approved for bottom board repairs!

Duct Tape is not an approved material for repairing bottom board.

If you are a professional installer that is using the Complete Installation Checklist for every home you install, you already know that there is a line item for bottom board holes and tears.

I hope that installers, retailers, community owners, and consumers are on the lookout for cable television, telephone, or satellite dish service technicians that have no respect for the importance of the bottom board under our homes. Their all too common practice of slicing open the bottom board to fish their cables and wires, must stop!

Bottom Board cut in two places for fishing cables.

Finally, many savvy industry professionals are now performing annual service inspections on their customer’s homes. For those of you that provide this service, make sure bottom board repair/patching is on your inspection checklist. If you don’t offer annual service inspections, maybe you should. It can be a money maker for you, and a money saver for your customers.

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It seems that at every installation training or seminar I present, installers and retailers complain that the home manufacturer is not providing the materials needed to complete the drain lines under the manufactured home. So I decided to take a look at this issue and see what we can learn.

The first thing we need to do is see exactly what the Manufactured Home Construction & Safety Standards (HUD Code) says about this.

Check out 24 CFR 3280.610(c)(1)-Drainage systems:

Each manufactured home shall have only one drain outlet.

Ok, now check out 24 CFR 3280.610(c)(5) Preassembly of Drain Lines:

Sections of the drainage system, designed to be located underneath the home, are not required to be factory installed when the manufacturer designs the system for site assembly and also provides all materials and components, including piping, fittings, cement, supports and instructions necessary for proper site installation.

So, when you look at both sections together, it should be pretty clear. The manufacturer is going to design the drainage system so that all of the individual drain line drops through the floor can be connected to one point AND they must provide all the materials needed for the installer to complete the drainage system according to the provided design.

To know that you are getting all the plumbing parts you are required to receive, you need to look at the design supplied with each new manufactured home shipped from the factory. Generally, this DAPIA approved design is included with the box of other shipped loose parts needed to complete the home. Following this design, you should be able to connect all of the drain line drops to that required “one drain outlet” with materials provided by the manufacturer.

The materials needed to complete the plumbing in the circled area would be shipped loose inside the home.

There is another reason it is important that the manufacturers supply installers with the needed parts and designs to complete the drain line, and it is called “preemption”. HUD has ruled (in a letter dated 12-4-1996) that state or local code enforcement may not require licensed plumbers to assemble shipped loose plumbing. But if you are not installing the drainage system according to the Manufactured Home Construction and Safety Standard, (by not following the DAPIA approved design, or using your own materials) then the local code requirements could apply.

It is important to note that where the drain lines from the home connect to the main sewage connection the local authority has control, and at that connection, a licensed plumber can be required.

If you are installing manufactured homes in an area that requires licensed plumbers to assemble the drain system, you should consider working with the manufacturers, your state officials, and possibly HUD to end this unnecessary requirement.

If your manufacturer is not shipping these required drain line parts with the home, you should show him 24 CFR 3280.610(c)(5). This is just one more reason why it is important for professional installers to know the HUD Code!

I hope this information is helpful.

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Having just wrapped up a week of talking to building code officials in three different states, I was reminded of the importance of the building permit application process and how professional installers need to improve the flow of information between themselves and the building code officials.

Far too many installers continue to pretend that the entire installation process for a manufactured home can be boiled down to a one-page pier print. Then complain if the code official doesn’t uniformly enforce installation requirements on other installers. The problem is that it is very difficult to organize the documents needed into a manageable sized packet of information. The typical installation manual is far too cumbersome and code officials are not going to spend time flipping through these 100+ page manuals for each permit application. Nor should they!

I thought if we could create a tool to help assemble a packet of designs, extracted from the manufacturer’s installation instructions, it could streamline the process, focus on the important issues of support and stabilization and help eliminate bad actors from the business of manufactured home installation. This post is intended to help installers assemble just such an informational packet through the use of a cover-sheet to pull everything together!

I know you don’t think you have the time to organize all the documents needed for a complete building permit application, or that the code official doesn’t want anymore then the one page pier print. But if we are ever going to move the manufactured housing industry and careers as professional installers forward, we need to look at the bigger picture when it comes to working with building code officials.

Here are a few things to consider:

Manufactured homes have gotten significantly more sophisticated over the years, yet our approach to working with the building code officials remains unchanged! If we want to improve the image of manufactured housing and attract a larger segment of the home buying public, we need to earn the confidence of the code officials.

Getting familiar with charts like this is step #1 to a more professional installation

As a trained and licensed professional installer, you should take charge of your installations by being in control of all of the documents needed to properly install the home. The way we have always done things in the past is probably wrong, out dated, and a waste of money and time. Housing designs have changed rapidly over the years, both installers and code officials must be on top of these changes. The only way to keep up with the changes is to make sure we are submitting and following current and pertinent installation documents with every permit application. We just lacked a tool to help installers organize the designs they need for a building permit.

Are there unlicensed installers stealing work from you? Once building code officials start seeing exactly what is to be expected for every building permit and subsequent installation, unlicensed installers will not be able to keep the pace.

Most importantly, a properly applied for building permit eliminates variables and unknowns from the process and goes a long way in increasing profits and reducing liability.

Ok…here is a breakdown on what should be included at permit application as a minimum:

Identify the licensed installer! Show the code official your license so that they come to expect a licensed installer for every new manufactured home installation.

Identify the home by manufacturer as well as home width, side wall height, roof pitch, foundation type and for a few manufacturers, the size of the eaves along the sidewall.

A copy of the manufacturer’s DAPIA approved installation instructions that highlight the appropriate charts and tables needed to construct the foundation. If not submitting the entire installation manual and only the table of contents page shows the DAPIA stamp, provide a copy of that page as well.

Provide DAPIA approved documents from the manufacturer that show approval for any alternate installation methods you might be using (such as alternative anchoring system or shallow frost protected foundation).

Include the Complete Installation Checklist from the installation manual or a Expanded Installation Checklist(from October 16, 2017 post) to better address the installation.

Provide notes on the soil bearing capacity, frost depth and other site-specific considerations that are needed to assure a proper installation.

Typical Pier Print-an installation tool, but must be used with several other design details.

And finally, prepare a plan of the home where you can layout the proper location of piers. CAUTION! Pier prints from the manufacturer are not to be trusted. Every pier print refers the installer to the actual installation instructions. You may want to use the pier print as a tool to help you determine pier locations, but never trust these pier prints without first reviewing it yourself!

You will likely need to add some additional documents for the code official (plot plan, sewer tap permits, etc.), but the cover sheet in the above link, will help you get the home specific details in order. Consider making this a part of your typical building permit procedure. I promise, if you try it one time you will quickly see the benefit!

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So far this month, I have had the chance to work with over 50 professional installers over several different training opportunities. One thing that became evident is that we all need to improve our understanding of the most basic part of a manufactured home foundation, the piers and footings.

When examining our support piers, I think it best to drill down to the bottom and work our way up. And at the bottom of every pier is the footing. Basically, the job of the footing is to spread the pier load in a way that keeps the pier from sinking into the earth (I like to compare a footing to a snow shoe. It keeps you from sinking into the snow by spreading out your body weight over a larger area).

There are three things you need to consider when you are determining what size and type of footing to use:

1.How much weight will the footing have to support?

2.How much weight can the ground under the footing support?

3.Will the footing shift or heave due to frost penetrating under the footing?

To be straight with you, there is a lot of information in our industry that is peppered with wiggle words and qualifiers that can mislead or misguide professional installers. I will do my best to just give you the facts based in the building science that I have examined.

Typical Pier Load Chart

In general, a pier supporting the manufactured home along the frame (you may call it the chassis), spaced every 8’ will need to support approximately 5,500 lbs. in the South roof load zone. If you are installing the home in the north roof load zone, you are looking at up to 6,900 lbs. These loads include the actual weight of the home, the assumed weight of people, furniture, the other contents inside the home (live load), and the anticipated weight of snow on the roof. The pier load charts in the manufacturers installation instructions are where you will find the actual load per pier. Since most of the country is in the South roof load zone, we will assume that each of our piers will need to carry 5,500 lbs.

Unfortunately, too many professional installers don’t put much thought into how much weight the soil can carry (AKA Soil Bearing Capacity). So either they use the default approach, or just do it the way they have for years. The default approach is found in the International Residential Code and referenced in the manufacturers installation instructions. This basically allows you to assume 1,500 lbs. per square foot soil bearing capacity for a decent, typical, well drained site.

So, if my pier load is 5,500 lbs., and my soil can carry 1,500 lbs. per square foot, I need to spread the load out over 3.6 square feet of earth (5,500 ÷ 1,500 =3.6). But you should go to the charts in the installation instructions where the math is done for you. This chart shows a 24” x 24” footing is needed, slightly larger than the 3.6 we calculated.

Footing must be smooth and flat! This is certain to fail!

If your footings are poured in place concrete, they must be at least 6” thick and depending on the load and soil bearing capacity, possibly thicker. The chart above requires our footing to be 8″ thick.

Poorly constructed footing

When you order the concrete, make sure the “footing mix” you request is 28-day compressive strength of 3,000 psi. In checking with a few concrete suppliers, there was some variation. Be certain that you finish the concrete to provide a flat, smooth, and level surface for the pier to rest.

If you use pre-cast concrete, they must be at least 4″ thick, meeting with the ASTM standard C90-02a. Patio slabs from the garden center generally do not meet this standard.

Listed and labeled ABS plastic footing pads can be used where protection from frost has been provided, or if the pad is placed below the maximum frost penetration line.

Ok, so we now know that our load on the pier is 5,500 lbs., and our footing will need to be 2 feet square as determined from the chart. But what about the construction of the actual pier? Almost every installation manual states that a single 8” x 16” concrete block can carry 8,000 lbs. (just stay under 36″ high). So, your pier can be constructed with single blocks that can easily carry the 5,500 lbs. load (If you are installing a Clayton product, they limit a dry stack, single block pier to 5,760 lbs.). Make certain you look at the specific installation instructions for the home you are installing.

In the Middle and North roof load zones, the piers loads are a little greater, and remember that not every home is the same! Next week we will talk about frost protection, the cap blocks, shims, and spacers that are needed to complete pier construction.